Question: The grades on a chemistry midterm at Covington are normally distributed with $\mu = 66$ and $\sigma = 5.5$. Omar earned a $67$ on the exam. Find the z-score for Omar's exam grade. Round to two decimal places.
Answer: A z-score is defined as the number of standard deviations a specific point is away from the mean We can calculate the z-score for Omar's exam grade by subtracting the mean $(\mu)$ from his grade and then dividing by the standard deviation $(\sigma)$ $ { z = \dfrac{x - {\mu}}{{\sigma}}} $ $ { z = \dfrac{67 - {66}}{{5.5}}} $ ${ z \approx 0.18}$ The z-score is $0.18$. In other words, Omar's score was $0.18$ standard deviations above the mean.